The Vatican document explicitly saying Catholic priests can bless same-sex unions lays out the conditions for what such blessings can, and cannot, involve.
The overall goal is to make it abundantly clear to the couple and those around them that the blessing in no way resembles a marriage. This is because the Catholic Church teaches that marriage is a lifelong union between a man and a woman.
Nothing has changed about the church’s position on marriage, its firm opposition to gay marriage, or its belief that any extramarital sex - gay or straight - is sinful.
What does the document say?
The document from the Vatican’s doctrine office explicitly says priests can offer blessings to same-sex couples provided the blessings themselves don’t in any way resemble a marriage. To avoid any confusion, the blessing should not be offered in conjunction with a civil union ceremony, gay or straight.